1. Field of the Invention
The present invention relates to a method of recognizing a character in which a process of correcting an inclination of a character in accordance with a predetermined evaluation value which indirectly indicates the inclination of the character, and then specifying the character area and extracting the feature of the character. Furthermore, the present invention relates to a character recognizing apparatus for carrying out this method.
2. Description of the Related Art
Technical Report PRU 94-100 pp. 25-30 of The Institute of Electronics Information and Communication Engineers discloses xe2x80x9cCorrection of Standard Line And Correction of Inclination for Recognizing Handwritten English Wordxe2x80x9d for tracking a contour line and then estimating an inclination of a character from a frequency of its moving direction. If a stroke for a character is one, it is possible to theoretically determine a calculation equation for specifying a direction of a stroke, determination for a plurality of strokes.
However, in this method, an erroneous inclination direction is outputted if a rate of the oblique stroke of the character is not uniform. For example, in a case of a character string of xe2x80x9cVANxe2x80x9d, both of xe2x80x9cVxe2x80x9d and xe2x80x9cAxe2x80x9d are bilaterally symmetrical. Thus, it is possible to correctly determine the inclination direction of the character. On the other hand, since xe2x80x9cNxe2x80x9d has a stroke in the right downward direction. It is judged that a central line is inclined in the right downward direction overall.
Other than the above-mentioned method, a method is well known which determines the directional distribution of longitudinal strokes of a character and thereby estimates the inclination direction of the character from its most possible value and average value. However, this method has the same problem as the above-mentioned method in principle.
Furthermore, a method of recognizing a character is disclosed in Japanese Patent Laid-open JP-A H05-242297 and JP-A H10-307889.
An object of the present invention is to provide a method for omitting a process of a character inclination correcting process for a character to be recognized.
Another object of the present invention is to provide an apparatus which can be used for omitting a process of a character inclination correcting process for a character to be recognized.
Still another object of the present invention is to provide a medium with a program for a method of omitting a process of a character inclination correcting process for a character to be recognized.
In order to achieve an aspect of the present invention, a method of recognizing a character, includes specifying a character image of an image corresponding to a character, evaluating symmetry of the character image, carrying out an inclination correcting process for the character image to produce a corrected character image, when the symmetry of the character image is not detected and executing a character recognizing process to the corrected character image.
In the above, said charring out includes carrying out the inclination correcting process to correct an angle of the character image such that a symmetrical axis of the character image is oriented to a vertical axis.
In order to achieve another aspect of the invention, a method of recognizing a character, further includes generating a mirrored replica image of the character image; and comparing the character image and the mirrored replica image.
In the above, the evaluating is carried out based on the comparing result.
In the above, the comparing is carried out a raster scanning unit.
In order to achieve another aspect of the invention, a method of recognizing a character, further includes overlapping the character image and the mirrored replica image.
In the above, the evaluating of the symmetry of the character image includes counting image dots overlapping between the character image and the mirrored replica image.
In the above, the inclination correction process is carried out, when the count is larger than a predetermined threshold value.
In the above, the character image is a part of a character string image.
In order to achieve aspect of the invention, a character recognizing apparatus includes a character candidate specifying unit specifying a character image of an image corresponding to a character, a symmetry evaluating device evaluating symmetry of a the character image and an inclination correcting unit carrying out an inclination correcting process for the character image to produce a corrected character image, when the symmetry of the character image is not detected and a character recognizing unit executing a recognizing of the corrected character image.
In the above, the inclination correcting unit corrects an angle of the character image such that a symmetrical axis of the character image is oriented to a vertical axis.
In order to achieve another aspect of the invention, a character recognizing apparatus includes an image inverter generating a mirrored replica image of the character image and a threshold comparator comparing the character image and the mirrored replica image.
In the above, the symmetry evaluating device carries out the evaluating based on the comparing result.
In the above, the threshold comparator carries out the comparing for a raster scanning unit.
In the above, threshold comparator overlaps the character image and the mirrored replica image.
In the above, the symmetry evaluating device counts image dots overlapping between the character image and the mirrored replica image.
In the above, the inclination correcting unit carries out the inclination correction process, when the count is larger than a predetermined threshold value.
In the above, the character image is a part of a character string image.
In order to achieve another aspect of the invention, a character recognizing apparatus includes a character candidate specifying unit specifying a character string image of an image corresponding to a character in an image, a symmetry evaluating device evaluating symmetry of character images of the character string image, an inclination correcting unit carrying out an inclination correcting process for the character string images to produce a corrected character image, when the symmetry in each of character images are not detected and a character recognizing unit executing a recognizing of the corrected character image.
In the above, the inclination correcting unit corrects an angle of the character string image such that symmetrical axis of the character images are oriented to a vertical axis, to produce a corrected character string image.
In order to achieve still another aspect of the invention, a character recognizing apparatus includes an image inverter generating a mirrored replica string image of the character images of the character string image and a threshold comparator comparing the character string image and the mirrored replica string image.
In the above, the symmetry evaluating device carries out the evaluation based on the comparing result.
In the above, the threshold comparator carries out the comparing for a raster scanning unit.
In the above, the threshold comparator overlaps the character string image and the mirrored replica string image.
In the above, the symmetry evaluating device counts image dots overlapping between the character string image and the mirrored replica string image.
In the above, the inclination correcting unit carries out the inclination correction process, when the count is larger than a predetermined threshold value.
In order to achieve aspect of the invention, a medium with a program for a method of recognizing a character includes a module specifying a character image of image corresponding to a character, a module evaluating symmetry of a the character image, a module carrying out an inclination correcting process for the character image to produce a corrected character image, when the symmetry of the character image is not detected and a module executing a character recognizing process to the corrected character image.
In the above, the module of the inclination correcting process corrects an angle of the character image such that a symmetrical axis of the character image is oriented to a vertical axis.
In order to achieve another aspect of the invention, a medium with a program for a method of recognizing a character further includes a module generating a mirrored replica image of the character image and a program comparing the character image and the mirrored replica image.
In the above, the module of the evaluating is carried out based on the comparing result.
In the above, the module of the comparing is carried out a raster scanning unit.
In the above, the module of the comparing includes a program overlapping the character image and the mirrored replica image.
In the above, the module of the evaluating the symmetry of the character image includes counting image dots overlapping between the character image and the mirrored replica image.
In the above, the module of the inclination correction process is carried out, when the count is larger than a predetermined threshold value.
In the above, the character image is a part of a character string image.
The present invention can refer to firstly several characters to thereby omit the inclination correcting process for the character string for which the inclination correction is obviously unnecessary. Especially, if character strings having inclinations partially exist in a large amount of character strings, the present invention can reduce the entire throughput, as compared with the case that the correction process is performed on all the character strings.